Fuel Cells and Fuel Cell Systems

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Fuel Cells and Fuel Cell Systems

• ME 1065
• L. Schaefer

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Proton Exchange Membrane

• Cathode ½O2 2 e- 2 H gt H2O
• Anode H2 gt 2 H 2 e-
• Overall H2 1/2 O2 gt H2O

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Problems with PEMs/PEFCs
Hydrogen Tank Rupture
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Direct Methanol

• Cathode 3/2 O2 6e- 6H gt 3 H2O
• Anode CH3OH H2O gt 6H CO2 6e-
• Overall CH3OH 3/2 O2 gt 2 H2O

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DMFCs, cont.
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Alkaline

• Cathode 1/2 O2 H2O 2e- gt 2 OH-
• Anode H2 2(OH)- gt 2H2O 2 e-
• Overall H2 1/2 O2 gt H2O

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AFCs, cont.
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Phosphoric Acid

• Cathode ½ O2 2 H 2 e- gt H2O
• Anode H2 gt 2H 2e-
• Overall H2 1/2 O2 gt H2O

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Molten Carbonate

• Cathode 1/2 O2 CO2 2 e- gt (CO3)
• Anode H2 (CO3) gt H2O CO2 2 e-
• Overall H2 1/2 O2 CO2 gt H2O CO2

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MCFCs, cont.
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Solid Oxide

• Cathode 1/2 O2 2 e- gt O
• Anode H2 O gt H2O 2 e-
• Overall H2 1/2 O2 gt H2O

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SOFCs, cont.
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Basic Summary of Four Types
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Fuel Cell Summary
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Fuel Cell Governing Equations

• Heat/Mass Transfer
• Electrochemical
• Electrical Network

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Governing Equations

• Heat and Mass Transfer Model
• Continuity, Momentum, Energy, Concentration

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Governing Equations

• Heat and Mass Transfer Model, cont.
• Continuity, Momentum, Energy, Concentration

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Hydrogen Fuel Cell Values
Form of Water Product Temp (C) Gibbs Free Energy of Formation (kJ/mol) Max EMF (V) Efficiency Limit ()
Liquid 25 -237.2 1.23 0.83
Liquid 80 -228.2 1.18 0.80
Gas 100 -225.3 1.17 0.79
Gas 200 -220.4 1.14 0.77
Gas 400 -210.3 1.09 0.74
Gas 600 -199.6 1.04 0.70
Gas 800 -188.6 0.98 0.66
Gas 1000 -177.4 0.92 0.62
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Performance Curves
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Fuel Cell Buses
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Hybrid Power
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Cogeneration and Cascading Energy Systems
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Unexpected Places!
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Figure for Example Problem